Arc lamp starter



.uly 5, 1966 H. G. HEINE EI'AL 3,259,797

ARC LAMP STARTER Filed Dec. 5, 1962 INVENTORS HANS c. HEINE OTTO E. LIENHARD ATTORNEY United States Patent 3,259,797 ARC LAMP STARTER Hans G. Heine, Northfield, Ill., and Otto E. Lienhard,

Upper Montclair, N..l., assiguor to Engelhard Industries, Inc., Newark, N..l., a corporation of Delaware Filed Dec. 5, 1962, Ser. No. 242,458 1 Claim. (Cl. 315-174) The present invention relates to starters for are lamps and particularly to starters for high pressure arc lamps operated by alternating current.

In a high pressure arc lamp the electrodes for producing the are are sealed in a pressurized atmosphere of an ionizable gas, such as Xenon, along with mercury which is vaporized when the lamp heats up. Starting the arc of such a lamp normally requires much higher voltage than the voltage necessary to operate the lamp.

The high voltage necessary to start the lamp is conveniently supplied by a well known pulse type ignition circuit comprising an ignition reactive transformer, a spar gap, a capacitor, and a radio frequency (RF) transformer. Such a circuit, typically operated on 115 volts, 6O cycle alternating current, produces during every half cycle of the line frequency radio frequency pulses with a peak voltage of up to 50,000 volts and a frequency of several megacycles per second. These pulses, if applied to the lamp at the proper time, are effective in starting xenon and mercury-xenon arc lamps.

Examination of current and voltage of an AC. operated arc lamp shows that current flows through the lamp while the voltage is near its peak value-that is, for not more than about 50% of the time.

The starter, of course, only delivers high voltage impulses when sufiicient voltage builds up at the spark gap to produce a spark. The impulses are therefore produced at the upper portions of the peaks and at the lower portions of the valleys of the cyclic voltage applied to the starter. In practice, the starter produces the high voltage pulses required to ionize the gap between the lamp electrodes and thus start the lamp only during about one half of each cycle or about 50% of the time.

It will therefore be appreciated that for the lamp to be started the voltage delivered by the starter must be in phase with the voltage at the lamp to the extent that the high volage impulses from the starter are applied to the lamp at the moment when the voltage to the lamp is at or above the minimum value at which current can flow through the lamp. In practice, it has been established that if the phases diifer by much more than about 50% the lamp will not start. Most efiicient starting occurs when the phase difference is somewhere between 0 and 50%. The exact point is determined by the size and capacity of the elements of the starter.

It is customary and desirable to operate the lamp and the starter from the same source of current. The elements normally included in the lamp circuit and starter circuit, however, throw the high voltage impulses delivered by the starter out of phase with the voltage in the lamp circuit.

It is desirable to have the starter shut off automatically as soon as the lamp starts. If it were to stay on, the current consumed would be increased and the excess wear on the elements of the starter would make it necessary to use more expensive and bulkier elements to withstand the wear. Furthermore, it is desirable to shut 01f the starter as quickly as possible in order to minimize radiofrequency interference connected with the high voltage pulses produced by the starter. With the proper balance of elements, the starter of the type described above will shut off automatically when the lamp starts.

Specifically, the lamp circuit normally includes ballast, such as a resistor, and the starter is connected across the "ice lamp circuit on the lamp side of the ballast. When the lamp starts the voltage drop at the ballast reduces the voltage to the starter. Therefore, the spark gap and other elements of the starter may be adjusted and proportioned so that the voltage to the spark gap will be insuflicient to operate it after the drop. Providing automatic shut oif of the starter in this manner, however, limits the extent to which the size and capacity of the starter can be altered as a means to adjust or compensate for the phase difference discussed above.

In accordance with the present invention means is provided for changing and adjusting the phase of voltage deliver d by the starter to coincide with the phase of the lamp voltage to the degree which will result in the quickest starting. The lamp and starter operate from the same source of current and the phase adjustment is made without sacrificing automatic shutoff of the starter when the lamp starts. In accordance with the invention, a capacitor and a resistor are in parallel with each other in one of the conductors between the starter and the source of current.

It is a principal object of the present invention to provide an improved starter for alternating current high pressure are lamps which includes simple and effective means for adjusting the phase of the voltage impulses from the starter thereby to be able to adjust the phase to overlap the phase of current and voltage to the lamp to the extent necessary to start the lamp most efiiciently.

It is a further object to provide such a starter which can be operated from the same source of current as the lamp and which will shut off automatically when the lamp starts.

Further objects and advantages of the device of this invention will be apparent from the following descrip tion and the accompanying drawing in which:

FIGURE 1 is a schematic drawing of the circuit of the starter of this invention and of the lamp with which the starter is operatively associated.

FIGURE 2 is an oscilloseopic diagram showing the wave characteristics of the voltage at the lamp and of the voltage delivered by a starter before phase adjustment.

FIGURE 3 is a diagram similar to FIGURE 2 but showing the wave characteristic of the voltage delivered by a starter after phase adjustment in accordance with the present invention.

Referring to FIGURE 1 of the drawings, the lamp 1 is a high pressure are lamp in which the lamp electrodes, not shown, are sealed under pressure in a quartz bulb with mercury and a rare ionizable rare gas, such as xenon. The lamp 1 is connected by leads 2 and 3 to a source of alternating current.

Also in the circuit of the lamp 1 are a resistance or ballast 4, in series in lead 2, and the secondary coil 5 of a radio frequency transformer 6, in series in lead 3. The coil 5 is part of the starter of this invention described below. A capacitor 7 is connected across the lamp, being connected to lead 2 at a point between the ballast 4 and the lamp 1 and to lead 3 at a point between the coil 5 and the source of current. This is a conventional lamp circuit and elements and arrangements described are well known.

The starter of this invention comprises generally, an RF (radio frequency) transformer 6 and a reactive transformer 8 between which are connected a spark gap 10 and a capacitor 11. The RF transformer 6 is formed by the secondary coil 5 and a primary coil 9. The spark gap 10 is connected in parallel with the coil 9 and the capacitor 11 is connected in series bet-ween the primary coil 9 and one end of the spark gap 10. A secondary coil 12 of the reactive transformer 8 is connected in parallel to the primary coil 9 of the RF transformer 6.

The reactive transformer 8 consists of the secondary coil 12 and a primary coil 13 around a core 14. Leads 15 and 16 from the ends of the primary coil 13 connect the reactive transformer 8 across the lamp circuit on the lamp side of the ballast 4.

In accordance with the present invention, the means for shifting and adjusting the phase of the impulses delivered by the starter comprise a capacitor 17 and a resistor 18 which are in parallel relation to each other and connected in series between the primary coil 13 and the source of current. This combination of capacitor and resistor shifts the phase. Fine adjustment of the phase shift is accomplished by selecting the size and capacity, of the resistor and capacitor used.

The size and ratings of the elements of a specific lamp circuit and of a starter in accordance with the present invention used therewith to accomplish efiective phase adjustment are set forth at the end of this description. It will, of course, be understood that the phase of the pulses from the starter is also determined by the size rating and adjustment of the RF transformer 6, the spark gap 10, the capacitor 11 and the reactive transformer 8. Consequently, the size of the capacitor 17 and resistor 18 which will provide the most effective phase adjustment cannot be determined unless the size and rating of the other elements of the starter are known.

As previously mentioned, the lamp 1 is only in condition to be started when the voltage to the lamp is at or near peak intensity or for about 50% of the time. Referring to FIGURES 2 and 3 which are oscilloscopic diagrams, the sine wave of the voltage at the lamp 1 is represented by the line 20. The wave characteristics of the voltage delivered to the lamp by the starter are represented by the line 21. As illustrated, the starter produces a series of high voltage impulses when the voltage to the starter is at peak intensity. These high voltage impulses are represented by spikes 22 in the line 21.

The duration, frequency, and intensity of the high voltage impulses of spikes 22 are determined by the size of the elements of the starter and adjustment of the spark gap 10. It would be possible to provide a starter which would deliver high voltage impulses sufficient for starting the lamp 1 almost continually. Of course, if high voltage impulses are delivered more or less continuously no phase adjustment would be necessary. However, to provide such an arrangement would require larger, more expensive elements and starter would not be adjusted to shut off automatically when the lamp starts.

To provide for automatic shut off of the starter the operative characteristics of the elements of the starter must be such that the spark gap 10 will not receive enough voltage to operate after the lampl is operating. The starter circuit, as previously mentioned, is preferably across the lamp circuit so as to be operated from the same source. As shown in FIGURE 1, the ballast 4 is effective in both circuits. Thus, when the lamp starts the voltage through the starter circuit drops. Automatic shut off of the starter is provided by selecting and adjusting the spark gap 10 to operate effectively on the voltage to it when the lamp is otI, but not operate on the reduced voltage to it after the voltage drop. In practice, a starter with a spark gap 10 operating in this manner can only be adjusted to produce high voltage impulses sufiicient for starting the lamp 1 at the points of highest intensity of the cyclic voltage to the starter. In FIG- URES 2 and 3 the high voltage impulses delivered by a starter operated in this manner are illustrated by the series of spikes 22 in the line 21.

Referring to FIGURES 2 and 3, the periods when the voltage at the lamp 1 is sufiicient for the lamp to be started are indicated by the portions of the line voltage wave line 20 rising above the dash line 24 and dipping below the dash'line 25. The periods when the starter delivers high voltage impulses or spikes 22 to the lamp are similarly indicated by the portions of the starter voltage wave line 21 rising above the dash line 24 and extending below the dash line 25. For the lamp 1 to be star-ted portions of the wave lines 20 and 21 must be above the dash line 2 and below dash 25 at the same points. As shown in FIGURE 2 the wave lines 20 and 21 are above and below dash lines 24 and 25 at ditferent times. Consequently, the lamp 1 will not start. It is therefore .necesary to adjust the phase of voltage from the starter to coincide with the phase of voltage at the lamp so that the phases coincide to an extent illustrated in FIGURE 3.

An impulse starter operated from the same current source at the lamp and comprising a radio frequency transformer 6, a spark gap 10, a capacitor 11, and a reactive transformer 8 will throw the voltage delivered from the starter out of phase with the current and voltage through the lamp. Oscilloscope examination of this situation would show a wave picture approximately similar to the wave picture shown in FIGURE 2.

The incorporation in the starter of a capacitor 17 and a resistor 18 in accordance with the present invention corrects the phase difference so that the wave picture looks like the wave picture shown in FIGURE 3 and the starter will be efiective for starting the lamp.

In operation the lamp 1 and starter are turned on by a switch or switches, not shown, which may be of any conventional type. Since. the starter of the present invention is adapted to be operated from the same current source as the lamp and is also adapted to shut off auto matically when the lam starts, the lamp and starter may be opearted by a single switch.

When the current is turned on current flows to the lamp and to the starter. The current through the starter is increased in voltage by the reactive transformer 8 and the RF transformer 6. In addition to the RF transformer 6, due to the operation of the spark gap 10 and capacitor 11, deliver the current to the lamp in high frequency pulses which is the type of high voltage current most effective for starting a high pressure are lamp.

By way of illustration, the starter of this invention has proved to be a quick and reliable starter capable for starting 1,000 watt mercury-Xenon arc lamps whether cold or still hot from recent operation. It might also be mentioned that the structure and arrangement of the elements of the starter of thi invention provide a simple rugged and compact starter which, make it particularly suited for use on shipboard at sea where compactness is desired and where ability to withstand severe corrosive conditions and still operate reliably are important for the efiicient operation and safety of the ship.

A standard 1,000 watt mercury-xenon lamp normally has an operating voltage of 65 to 75 volts. A starter in accordance with the present invention adapted for use with this lamp is adjusted to operate at least volts and preferably volts. This is accomplished by adjusting the spark gap 10 of the RF transformer 6, which in this embodiment of the starter is a transformer with a turn ratio of 6 to 46. With such a ratio the spark gap would be set at 3 times 0.045 inch. The reactive transformer 8 associated with this RF transformer has a primary voltage of volts and a secondary open terminal voltage of 7500 volts with a primary of 115 volts.

In this embodiment the phase of current delivered by the starter is adjusted to overlap the phase of current through the lamp by use of a capacitor 1'7 rated at 20 microfarads and a resistor 18 of 200 ohms.

It will be understood that various modifications may be made in the structure, arrangement and size of the elements of the preferred embodiment of the starter described above without departing from the spirit of the invention expressed in the appended claim.

What is claimed is:

A starter for a high pressure are lamp comprising a source of alternating current, a :radio frequency transformer having a primary winding and a secondary winding connected in series with the lamp and across said source, a spark gap across said primary winding, a capacitor connected between the primary winding and the spark gap, a reactive transformer having a primary winding connected across said source and a secondary Winding connected in parallel with the spark gap, and a capacitor and a resistor in parallel relation to each other and connected in series to the primary winding of the reactive transformer.

References Cited by the Examiner UNITED STATES PATENTS 2,151,786 4/1939 Marbury 315--163 6 2,399,33 1 4/ 1946 Denault 315-174 2,431,284 11/1947 Stadum 315194 2,985,795 5/ 1961 Bird 315174 DAVID J. GALVIN, Primary Examiner.

GEORGE N. WESTBY, Examiner.

K. CROSSON, R. JUDD, Assistant Examiners. 

